Embodiments of the device and method discussed herein relate to a system and method for manufacturing intracorporeal devices used to replace, strengthen, or bypass body channels or lumens of patients; in particular, those channels or lumens that have been affected by conditions such as abdominal aortic aneurysms.
Existing methods of treating abdominal aortic aneurysms include invasive surgical methods with grafts used to replace the diseased portion of the artery. Although improvements in surgical and anesthetic techniques have reduced perioperative and postoperative morbidity and mortality, significant risks associated with surgical repair (including myocardial infarction and other complications related to coronary artery disease) still remain.
Due to the inherent hazards and complexities of such surgical procedures, various attempts have been made to develop alternative repair methods that involve the endovascular deployment of grafts within aortic aneurysms. One such method is the non-invasive technique of percutaneous delivery of grafts and stent-grafts by a catheter-based system. Such a method is described by Lawrence, Jr. et al. in xe2x80x9cPercutaneous Endovascular Graft: Experimental Evaluationxe2x80x9d, Radiology (1987). Lawrence et al. describe therein the use of a Gianturco stent as disclosed in U.S. Pat. No. 4,580,568 to Gianturco. The stent is used to position a Dacrone(copyright) fabric graft within the vessel. The Dacrono(copyright) graft is compressed within the catheter and then deployed within the vessel to be treated.
A similar procedure is described by Mirich et al. in xe2x80x9cPercutaneously Placed Endovascular Grafts for Aortic Aneurysms: Feasibility Study,xe2x80x9d Radiology (1989). Mirich et al. describe therein a self-expanding metallic structure covered by a nylon fabric, the structure being anchored by barbs at the proximal and distal ends.
An improvement to percutaneously delivered grafts and stent-grafts results from the use of materials such as expanded polytetrafluoroethylene (ePTFE) for a graft body. This material, and others like it, have clinically beneficial properties. However, manufacturing a graft from ePTFE can be difficult and expensive. For example, it is difficult to bond ePTFE with conventional methods such as adhesives, etc. In addition, depending on the type of ePTFE, the material can exhibit anisotropic behavior. Grafts are generally deployed in arterial systems whose environments are dynamic and which subject the devices to significant flexing and changing fluid pressure flow. Stresses are generated that are cyclic and potentially destructive to interface points of grafts, particularly interface between soft and relatively hard or high strength materials.
What has been needed is a method and device for manufacturing intracorporeal devices used to replace, strengthen or bypass body channels or lumens of a patient from ePTFE and similar materials which is reliable, efficient and cost effective.
An embodiment of the invention is directed to a mold for manufacture of an endovascular graft, or section thereof, which has at least one inflatable channel or cuff. The mold has a plurality of mold body portions configured to mate with at least one other mold body portion to produce an assembled mold having a main cavity portion. The main cavity portion has an inside surface contour that matches an outside surface contour of the graft section with the at least one inflatable channel or cuff in an expanded state. In some embodiments, the main cavity portion may include channel cavities, cuff cavities, longitudinal channel cavities or helical channel cavities which are configured to correspond to inflatable channels, inflatable cuffs, inflatable longitudinal channels or inflatable helical channels of the graft when in an expanded state. In other embodiments, the mold can have a plurality of circumferential channel cavities and at least one longitudinal channel cavity or helical channel cavity that transects the circumferential channel cavities.
Another embodiment is directed to an outer constraint device in the form of a mold for manufacture of an endovascular graft, or section thereof, which has at least one inflatable channel or cuff. The mold has a first mold body portion having a main cavity portion with an inside surface contour that is live configured to correspond to an outside surface contour of the graft section with the at least one inflatable channel or cuff In an expanded state. The mold also has a second mold body portion configured to mate with the first mold body portion having a main cavity portion with an inside surface contour that is configured to correspond to an outside surface contour of the graft section with the at least one inflatable channel or cuff in an expanded state.
A further embodiment of the invention i s directed to a pressure line for use in the manu facture of an endovascular graft, or section thereof. The pressure line has an elongate conduit with an input end, an output end and a permeable section. The permeable section can have a permeability gradient which increases with distance from the input end. In one embodiment, the permeability of the pressure line increases about 5 to about 20 percent per centimeter in a direction from the input end to the output end along the permeable section. The permeability gradient in the permeable section can be created by a plurality of outlet orifices in the elongate conduit which increase in diameter with an increase in distance from input end. In addition, such outlet orifices can be spaced longitudinally from each other so as to match a longitudinal spacing of a plurality of circumferential inflatable channels of the endovascular graft.
Another embodiment of the invention includes a mandrel for shape forming an endovascular graft, or section thereof. The mandrel has a middle section and a first end section with at least a portion which has a larger outer transverse dimension than an outer transverse dimension of the middle section and which is removably secured to a first end of the middle section. A second end section is disposed at a second end of the middle section with at least a portion which has a larger outer transverse dimension than an outer transverse dimension of the middle section. In a particular embodiment, the first end section and second end section are removably secured to the middle section by threaded portions and a longitudinal axis of the first end section, second end section and middle section can be substantially coaxial. In another embodiment, the middle section can have a pressure line recess in the form of a longitudinal channel in an outer surface of the middle section which is configured to accept a pressure line.
Embodiments of the invention can include an assembly for manufacture of an endovascular graft, or section thereof, which has at least one inflatable cuff or channel on a section thereof. The assembly consists of a mandrel having an elongate body having an outer surface counter configured to support an inside surface of the graft section. The graft section having at least one inflatable cuff or channel is disposed about at least a portion of the mandrel. A pressure line having an elongate conduit with an input end, an output end and a permeability gradient which increases with distance from the input end is in fluid communication with an inflatable cuff or channel of the graft section. A mold is at least partially disposed about the graft section, the pressure line and the mandrel. The mold has a plurality of mold body portions configured to mate together to produce an assembled mold having a main cavity portion. The main cavity portion has an inside surface contour that matches an outside surface contour of the graft section with the at least one inflatable cuff or channel in an expanded state. The inside surface contour is configured to radially constrain an outer layer or layers of the at least one inflatable cuff or channel during expansion of the cuff or channel. In some embodiments, the plurality of orifices of the elongate conduit of the pressure line can be substantially aligned with circumferential channel cavities of the mold.
Embodiments of the invention which include methods for forming an inflatable channel or cuff of an endovascular graft, or section thereof, will now be described. An graft section is provided with at least one inflatable channel or cuff formed between layers of graft material of the graft section in an unexpanded state. A mold is provided which has a main cavity portion with an inside surface contour that corresponds to an outside surface contour of the graft section with the at least one inflatable channel or cuff in an expanded state. The graft section is then positioned in the main cavity portion of the mold with the at least one inflatable channel or cuff of the graft section in an unexpanded state positioned to expand into corresponding channel or cuff cavity portions of the main cavity portion. Once the graft section is properly positioned within the main cavity portion of the mold, pressurized gas is injected into the at least one inflatable channel or cuff to expand the at least one inflatable channel or cuff. Thereafter, the graft material of the at least one inflatable channel or cuff is fixed with the at least one inflatable channel or cuff in an expanded state.
In a particular embodiment of the method, a pressure line having an elongate conduit with a permeable section which includes a permeability gradient can be placed in fluid communication with at least one inflatable channel or cuff of the graft section. Thereafter, pressurized gas can be injected into the at least one inflatable channel or cuff through the permeable section of the pressure line. In addition, an optional internal radial support can be positioned within the graft section prior to expansion of the at least one inflatable channel or cuff. The internal radial support may consist of a mandrel which is disposed within the graft section prior to placing the graft section into the mold so as to radially support the inside surface of the graft section during injection of the pressurized gas. In one embodiment, the graft material of the at least one inflatable channel or cuff is fixed by sintering. In another embodiment of a method for forming at least one inflatable channel or cuff of an endovascular graft, or section thereof, a pressurized liquid can be injected into the inflatable channel or cuff of the graft section. Some expansion of the inflatable channel or cuff can be carried out by vapor pressure from boiling of pressurized liquid during fixing of the graft material with the liquid in the inflatable channel or cuff.